The invention relates to a joint spindle arranged particularly in a drive of a rolling mill, which has a wobbler for effecting a connection with a joint head, or a joint head for effecting a connection with a wobbler, whose tongue engages in a cylindrical opening of the joint head extending transversely of the axis of rotation, wherein a sliding block is arranged between the joint head and the tongue, which sliding block is formed by two sliding bodies which have in partial areas thereof contours of a body of rotation, wherein the sliding bodies are arranged in a recess in the joint in such a way that they can carry out a pivoting movement in the joint head.
Sliding blocks, also called joint blocks, are known. The sliding block is composed of a non-metal or metal material, and is used in joint spindles and joint coupling heads of rolling mill drives. When using a joint block in the heads of the joint spindles arranged on both sides, or in the subsequent coupling heads, a flat pin of the spindle or of the head interacts with the joint block. The purpose of the joint blocks is essentially to carry out compensation with respect to length and direction between the joint spindles, which are changeable relative to each other within certain limits in their axial direction and the rigidly arranged coupling elements in the pinion and roll stand. In addition to the transmission of the high torques and the impact-like loads, as they occur during the start-up of the stands and primarily in very short sequences when tapping the rolling stock in the work rolls, the joint or sliding block has the added purpose of receiving additional relative movements under high surface pressures.
These various loads, many of which are superimposed, lead to a relatively quick and marked wear. Although it has always been attempted to increase the durability of the joint blocks by ever more suitable novel materials, for example, by the use of new materials, it is so far still necessary to frequently exchange the sliding blocks because of wear.
Aside from the costs of the replacement parts and the attendant storage capacity, and primarily because of the exchange of the sliding blocks, the time periods for idle and assembly times caused by the replacement of the sliding blocks are extremely long, because when exchanging the sliding blocks usually a complete separation of the joint spindles from the subsequent coupling elements is required. In the cost intensive rolling mill plants, the idle and assembly times caused by repairs are an extremely high burden, especially when they occur at unscheduled times.
For lowering these material costs, and especially for reducing the required material, a sliding block or joint block for joint spindles and joint coupling heads of rolling mill drives is known from DE 26 56 257 A1, which is composed of several partial sections. In this connection, dividing planes for the partial sections in the transverse direction of the longitudinal axis of the joint block are provided.
Moreover, WO 2004/072501 discloses a sliding block for giant spindles in drives of rolling mills, which permits a high surface pressure and, furthermore, also has a high resistance to heat. In this regard, the joint spindle has a wobbler with a flat pin whose tongue engages in a cylindrical opening of the spindle head extending transversely of the axis of rotation, wherein a sliding block is arranged between the spindle head and the flat pin. This sliding block is of a composite construction and has a metal inner body and an outer layer of polymer fiber material surrounding the inner body.
From GB 262 144 a joint spindle is known which effects a connection with an articulated head or with a wobbler. For this purpose, sliding blocks are used which have the shape of a truncated cone. GB 284 462 describes an articulated connection between a cam and a shaft in which elements with cylindrical surfaces are used.
The state of the art is illustrated in FIGS. 1 and 2. FIG. 1 shows in an exploded view a wobbler 2 equipped with a tongue 1 for connecting with a joint spindle 3.
FIG. 2 shows a sectional view perpendicular to the sectional view of FIG. 1 taken along sectional line II-II.
The joint spindle 3 has a joint head 4 which is equipped with a recess 5 for receiving the tongue 1. The tongue 1 is composed of two protruding elements 6, 7 forming a finger-shaped flat blade together with a cylindrical contour facing the outer side of the wobbler 1, and a parallelepiped-shaped contour facing the inner side of the wobbler 1. A sliding block 8 with two sliding plates 9, 10 is fastened on the elements 6, 7. The sliding plates 9, 10 have surfaces 11, 12 which rest in the recess 5 to make it possible that the sliding block 8 and the joint spindle can be turned or pivoted perpendicularly of the longitudinal axis x of the joint spindle 3 about an axis z. The surfaces 11, 12 are constructed in such a way that they fit into corresponding contours 13, 14 within the recess 5 in the joint head 4 of the joint spindle 3.
The joint blocks or sliding plates 9, 10 are connected to each other through a bolt 15 which protrudes into the wobbler recess formed by the elements 6, 7 and which generally is guided in a bore 16 or 17 in the sliding blocks 9 or 10, respectively. The relative movement between the joint head 4 and the wobbler 2 is carried out by the rotation of the sliding block 8 and by a pivoting movement of the elements 6, 7. The sliding plates 9, 10 must be guided through a stop, in order to prevent slipping of the sliding plates 9, 10 in the direction of the z axis. In a standard embodiment, a cylindrical groove 18 is provided for this purpose in the middle of the joint head 4 of a cylindrical groove 18 in which the sliding plates 9, 10 are placed with a guide cam 19.
In the past, it has been found that the increased output of the rolling plant causes stress fractures at these guide grooves.